Any way to trace a background pcb image?


#1

Hi, I remember Diptrace could do this when I flirted with it, just wondering if in Kicad Pcbnew I can load up a background pcb image (eg scanned from a magazine, or downloaded etc) and use it as a guide to place footprints & route it all together etc?

I have a pdf here with a pcb layout on it, would be handy if I could just load it into Pcbnew as a guide? But i don’t think I can, right?

I can use Pcbnew without bothering with schematics, yes?


#2

Not advisable but doable. In the interactive router you need to disable the drc check. (otherwise you can’t connect pads with different pads like you have without a netlist.)

If the pcb is that simple that you can work without a schematic, the schematic should only take a couple of hours do create. Having a schematic greatly reduces the probability do make errors. (And it makes it a lot easier for you to remember what you did a few month down the line.)

Any project where designing the schematic will take days is way to complex to design without the support of a schematic. (Or to put it another way: The probability of creating an error increases with the complexity of the board.)


#3

I hear ya. Thanks! I’ve toner-transferred the layout & proto-assembled it so I know it’s fine, but I want to run off a couple more, I hate toner-transferring so thought I’d spend a wholesome $10 at DirtyPCBs or something :stuck_out_tongue:

Thanks for reminder of turning off DRC check. I will just manually copy the layout without a background image.

Despite this teeny minor issue, I’m so glad I (a noobie hobbyist) invested my time in Kicad in the end, it’s great.


#4

If you can get any sort of image format, I would use bitmap2component tool in KiCad to create a module and use that as a template, delete it later.


#5

What you want to do is place the components in the same places and place the tracks “clean”.
Placing takes longer than tracking on most jobs


#6

If I understand the problem correctly, I think @bobc has the best answer, and @davidsrsb gives us a reason for why we may choose this workflow.

The OP (@mollux) hasn’t told us how complex the design is - he may even have access to a schematic or other design information, though not in KiCAD format - but he wants to create a close replica of an existing, proven good, layout. Perhaps the circuit has potential pitfalls (e.g., RF or high-speed signals; high voltage; high current; noise sensitivity; complex outline or cutouts; etc) that have already been solved and @mollux doesn’t want to re-invent those wheels. (A significant problem with re-inventing somebody else’s wheel is you are never sure that you have filed off all the corners. Some wheels have corners hidden in obscure places.)

Reducing the existing design to an image file(s), then using the image as a template for placement and routing seems a very reasonable approach. This may be true even if he has a KiCAD schematic and netlist; and if he doesn’t, then creating them really should be on his to-do list.

Dale


#7

There is one crazy idea I had : create a KiCad schematic from a PCB (or maybe other source). It would be a lot of work to get a really neat output (requiring image recognition and auto-layout), and the number of use cases is a bit limited. Perhaps it might still be useful to get a basic schematic which requires cleaning up.

Altium has a feature to reverse engineer from Gerbers, I wondered why would a company paying top dollar for Altium need that? It seems more suitable for a small copy shop “no questions asked!”. But then I thought about my company, and realised it is quite possible to lose all the design info for an old design, and maybe the only data is with the fab house who make the bare PCBs for us!


#8

What actually happens are two scenarios:
-that PCB projects are designed by sub contractors on their own CAD systems. They then supply you with Gerber plots and maybe proprietary CAD files for CAD software you don’t have.
-in house designers do a project on a CAD system and at some later date that CAD system is no longer operational, Windows versionitis or license key/dongle loss.

Years later you go back and want to work on that project


#9

Thanks for all your help, guys!

I ran into a problem. I loaded my pcb-layout image file into “bitmap2component” & it spat out a “.kicad_pcb” file that the Library Wizard didn’t recognize? I see that my old footprints folder all have “.kicad_mod” extensions? So I went & blindly changed my pcb-image file extension to “kicad_mod”, and now the Library Wizard recognizes it, I hit “Next” and Kicad crashes lol.

Any idea of what I’m doing wrong here?


#10
  1. no, it won’t spit out a kicad_pcb file ever.
  2. kicad_mod is the modern format.
  3. the library wizard is handling pretty folders that contain kicad_mod files (the folders are the libraries) or legacy format footprint library files that contain more than one footprint, etc…

using this:

like this (I didn’t care for DPI here, so result won’t have the correct scale in PCBnew):

get’s me this:

PCBV1_5.kicad_mod (100.5 KB)


#11

There is nothing RF sensitive or electrical safety clearance critical about that tracking.
What you do care about are board outline, fixing hole position and general component placement.


#12

I just took a random layout from the internet… this is not @mollux pcb.

He claims to get a kciad_pcb file, which means he did something wrong somewhere, so I guided him through the process…


#13

Thank you, Joan_Sparky. I tried again & it worked sweet. Not sure what I did wrong before. Anyhow now I have a “fake footprint” of my pcb-layout in the background, and i can place footprints & route them over the top. Success! Thanks again for the assistance.